Refactored SettingsCache to get events through DI

- requiring lib/common/events makes the settings cache tightly coupled to the server
- moving this up to settings index means the cache itself can be moved to a shared component/moved out of Ghost
- the index then becomes the settings manager
- questionable whether the event listeners & updater part of this shouldn't be part of a manager, independent of the actual cache 🤔

core/server/services/settings/cache.js

@@ -3,7 +3,6 @@
 // circular dependency bugs.
 const debug = require('@tryghost/debug')('settings:cache');
 const _ = require('lodash');
-const events = require('../../lib/common/events');
 const publicSettings = require('./public');
 
 // Local function, only ever used for initialising
@@ -110,12 +109,13 @@ module.exports = {
      *
      * Optionally takes a collection of settings & can populate the cache with these.
      *
+     * @param {EventEmitter} events
      * @param {Bookshelf.Collection<Settings>} [settingsCollection]
      * @return {object}
      */
-    init(settingsCollection) {
+    init(events, settingsCollection) {
         // First, reset the cache and listeners
-        this.reset();
+        this.reset(events);
 
         // // if we have been passed a collection of settings, use this to populate the cache
         if (settingsCollection && settingsCollection.models) {
@@ -132,8 +132,9 @@ module.exports = {
 
     /**
      * Reset both the cache and the listeners, must be called during init
+     * @param {EventEmitter} events
      */
-    reset() {
+    reset(events) {
         settingsCache = {};
 
         events.removeListener('settings.edited', updateSettingFromModel);

core/server/services/settings/index.js

@@ -2,6 +2,7 @@
  * Settings Lib
  * A collection of utilities for handling settings including a cache
  */
+const events = require('../../lib/common/events');
 const models = require('../../models');
 const SettingsCache = require('./cache');
 
@@ -27,14 +28,14 @@ module.exports = {
      */
     async init() {
         const settingsCollection = await models.Settings.populateDefaults();
-        SettingsCache.init(settingsCollection);
+        SettingsCache.init(events, settingsCollection);
     },
 
     /**
      * Shutdown the cache, used in force boot during testing
      */
     shutdown() {
-        SettingsCache.reset();
+        SettingsCache.reset(events);
     },
 
     /**

test/unit/services/settings/cache_spec.js

@@ -70,7 +70,7 @@ describe('UNIT: settings cache', function () {
             }]
         };
 
-        cache.init(settingsCollection);
+        cache.init(events, settingsCollection);
         cache.get('key1').should.equal('init value');
 
         // check handler only called once on settings.edit
@@ -83,7 +83,7 @@ describe('UNIT: settings cache', function () {
         cache.get('key1').should.equal('first edit');
 
         // init does a reset by default
-        cache.init(settingsCollection);
+        cache.init(events, settingsCollection);
         setSpy.callCount.should.equal(3);
         cache.get('key1').should.equal('init value');